Iodine-doped carbon nanotubes boosting the adsorption effect and conversion kinetics of lithium-sulfur batteries

Compared with lithium-ion batteries (LIBs), lithium-sulfur batteries (LSBs), based on electrochemical reactions involving multi-step 16-electron transformations provide higher specific capacity (1672 mAh g-1) and specific energy (2600 Wh kg-1), exhibiting great potential in the field of energy storage. However, the inherent insulation of sulfur, slow electrochemical reaction kinetics and detrimental shuttle-effect of lithium polysulfides (LiPSs) restrict the development of LSBs in practical applications. Herein, the iodine-doped carbon nanotubes (I-CNTs) is firstly reported as sulfur host material to the enhance the adsorption-conversion kinetics of LSBs. Iodine doping can significantly improve the polarity of I-CNTs. Iodine atoms with lone pair electrons (Lewis base) in iodine-doped CNTs can interact with lithium cations (Lewis acidic) in LiPSs, thereby anchoring polysulfides and suppressing subsequent shuttling behavior. Moreover, the charge transfer between iodine species (electron acceptor) and CNTs (electron donor) decreases the gap band and subsequently improves the conductivity of I-CNTs. The enhanced adsorption effect and conductivity are beneficial for accelerating reaction kinetics and enhancing electrocatalytic activity. The in-situ Raman spectroscopy, quasi in-situ electrochemical impedance spectroscopy (EIS) and Li2S potentiostatic deposition current-time (i-t) curves were conducted to verify mechanism of complex sulfur reduction reaction (SRR). Owing to above advantages, the I-CNTs@S composite cathode exhibits an ultrahigh initial capacity of 1326 mAh g-1 as well as outstanding cyclicability and rate performance. Our research results provide inspirations for the design of multifunctional host material for sulfur/carbon composite cathodes in LSBs.

Hypervalent Iodine (III)-Based Complexation for Chiroptical Supramolecular Glass, Deep Eutectic Solvent and Luminescent Switch

Hypervalent iodine(III) have widely been utilized for organic synthetic reagents. They are also recognized as positive charge-assisted, exceptionally robust biaxial halogen bond donors, while their potential in supramolecular materials is barely explored. This work reports a cyclic diaryliodonium ion as biaxial halogen bonding donor that displays remarkable binding affinity toward phenanthroline or acridine acceptors with chiral pendants. Biaxial halogen bonding enables chiroptical evolution in solution, allowing for rational control over supramolecular chirality. Leveraging their strong binding affinity, the halogen bonding complexes manifested amorphous properties and deep eutectic behavior in the solid state. Capitalizing on these attributes, this work achieves the successful preparation of supramolecular glasses and deep eutectic solvents. Additionally, halogen bonding appended light irradiation-triggered luminescence through a hydrogen atom transfer process, showing applications in anti-counterfeit and display.

Recent advances in the functionalization, substitutional doping and applications of graphene/graphene composite nanomaterials

Recently, graphene and graphene-based nanomaterials have emerged as advanced carbon functional materials with specialized unique electronic, optical, mechanical, and chemical properties. These properties have made graphene an exceptional material for a wide range of promising applications in biological and non-biological fields. The present review illustrates the structural modifications of pristine graphene resulting in a wide variety of derivatives. The significance of substitutional doping with alkali-metals, alkaline earth metals, and III-VII group elements apart from the transition metals of the periodic table is discussed. The paper reviews various chemical and physical preparation routes of graphene, its derivatives and graphene-based nanocomposites at room and elevated temperatures in various solvents. The difficulty in dispersing it in water and organic solvents make it essential to functionalize graphene and its derivatives. Recent trends and advances are discussed at length. Controlled reduction reactions in the presence of various dopants leading to nanocomposites along with suitable surfactants essential to enhance its potential applications in the semiconductor industry and biological fields are discussed in detail.

Breaking Mass Transport Limitations by Iodized Polyacrylonitrile Anodes for Extremely Fast-Charging Lithium-Ion Batteries

The fast-charging capability of rechargeable batteries is greatly limited by the sluggish ion transport kinetics in anode materials. Here we develop an iodized polyacrylonitrile (I-PAN) anode that can boost the bulk/interphase lithium (Li)-ion diffusion kinetics and accelerate Li-ion desolvation process to realize high-performance fast-charging Li-ion batteries. The iodine immobilized in I-PAN framework expands ion transport channels, compresses the electric double layer, and changes the inner Helmholtz plane to form LiF/LiI-rich solid electrolyte interphase layer. The dissolved iodine ions in the electrolyte self-induced by the interfacial nucleophilic substitution of PF6 - not only promote the Li-ion desolvation process, but also reuse the plated/dead Li formed on the anode under fast-charging conditions. Consequently, the I-PAN anode exhibits a high capacity of 228.5 mAh g-1 (39 % of capacity at 0.5 A g-1 delivered in 18 seconds) and negligible capacity decay for 10000 cycles at 20 A g-1 . The I-PAN||LiNi0.8 Co0.1 Mn0.1 O2 full cell shows excellent fast-charging performance with attractive capacities and negligible capacity decay for 1000 cycles at extremely high rates of 5 C and 10 C (1 C=180 mA g-1 ). We also demonstrate high-performance fast-charging sodium-ion batteries using I-PAN anodes.

Influence of halogen elements in organic salts on n-type doping of CNT yarn for thermoelectric applications

Doping control of carbon nanotube (CNT) is crucial for thermoelectric (TE) application to maximize the power conversion efficiency. Despite the recent achievement of good air stability by organic salts for n-type carrier doping, their doping mechanism has not been systematically investigated so far. Here, we demonstrate doping of CNT yarn using ammonium salts with different halogen elements (tetra-butylammonium salts, TBAX where X = Cl, Br, or I) through the dipping technique. By changing the halogen element, we specifically investigated the halogen effect in the n-type doping process of CNT. The introduction of each material into the CNT yarn and its doping reaction were then studied by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Halogen element was found to affect the excess amount of TBA⁺ cation in the CNT yarn. The largest amount of excess TBA⁺ is found in the TBAI-doped yarn, which stabilizes the most amount of negative charge in CNT, enhancing the TE performance and its stability over one month in air. This study discovers the importance of the halogen element in the doping process of CNT-based TE materials by organic salts, simultaneously offering an efficient and stable n-type doping strategy.

Impact of Iodine Electrodeposition on Nanoporous Carbon Electrode Determined by EQCM, XPS and In Situ Raman Spectroscopy

The charging of nanoporous carbon via electrodeposition of solid iodine from iodide-based electrolyte is an efficient and ecofriendly method to produce battery cathodes. Here, the interactions at the carbon/iodine interface from first contact with the aqueous electrolyte to the electrochemical polarization conditions in a hybrid cell are investigated by a combination of in situ and ex situ methods. EQCM investigations confirm the flushing out of water from the pores during iodine formation at the positive electrode. XPS of the carbon surface shows irreversible oxidation at the initial electrolyte immersion and to a larger extent during the first few charge/discharge cycles. This leads to the creation of functional groups at the surface while further reactive sites are consumed by iodine, causing a kind of passivation during a stable cycling regime. Two sources of carbon electrode structural modifications during iodine formation in the nanopores have been revealed by in situ Raman spectroscopy, (i) charge transfer and (ii) mechanical strain, both causing reversible changes and thus preventing performance deterioration during the long-term cycling of energy storage devices that use iodine-charged carbon electrodes.

Research Progress on Porous Carbon-Based Non-Precious Metal Electrocatalysts

The development of efficient, stable, and economic electrocatalysts are key to the large-scale application of electrochemical energy conversion. Porous carbon-based non-precious metal electrocatalysts are considered to be the most promising materials to replace Pt-based catalysts, which are limited in large-scale applications due to high costs. Because of its high specific surface area and easily regulated structure, a porous carbon matrix is conducive to the dispersion of active sites and mass transfer, showing great potential in electrocatalysis. This review will focus on porous carbon-based non-precious metal electrocatalysts and summarize their new progress, focusing on the synthesis and design of porous carbon matrix, metal-free carbon-based catalysts, non-previous metal monatomic carbon-based catalyst, and non-precious metal nanoparticle carbon-based catalysts. In addition, current challenges and future trends will be discussed for better development of porous carbon-based non-precious metal electrocatalysts.

Novel and Highly Sensitive Electrochemical Sensor for the Determination of Oxytetracycline Based on Fluorine-Doped Activated Carbon and Hydrophobic Deep Eutectic Solvents

Residues of oxytetracycline (OTC), a veterinary antibiotic and growth promoter, can be present in animal-derived foods; their consumption is harmful to human health and their presence must therefore be detected and regulated. However, the maximum residue limit is low, and consequently highly sensitive and accurate detectors are required to detect the residues. In this study, a novel highly sensitive electrochemical sensor for the detection of OTC was developed using a screen-printed electrode modified with fluorine-doped activated carbon (F-AC/SPE) combined with a novel deep eutectic solvent (DES). The modification of activated carbon by doping with fluorine atoms (F-AC) enhanced the adsorption and electrical activity of the activated carbon. The novel hydrophobic DES was prepared from tetrabutylammonium bromide (TBABr) and a fatty acid (malonic acid) using a green synthesis method. The addition of the DES increased the electrochemical response of F-AC for OTC detection; furthermore, it induced preconcentration of OTC, which increased its detectability. The electrostatic interactions between DES and OTC as well as the adsorption of OTC on the surface of the modified electrode through H-bonding and π-π interactions helped in OTC detection, which was quantified based on the decrease in the anodic peak potential (E _pa = 0.3 V) of AC. The electrochemical behavior of the modified electrode was investigated by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. Under optimum conditions, the calibration plot of OTC exhibited a linear response in the range 5-1500 μg L^-1, with a detection limit of 1.74 μg L^-1. The fabricated electrochemical sensor was successfully applied to determine the OTC in shrimp pond and shrimp samples with recoveries of 83.8-100.5% and 93.3-104.5%, respectively. In addition to the high sensitivity of OTC detection, the proposed electrochemical sensor is simple, cost-effective, and environmentally friendly.

Structural and Chemical Peculiarities of Nitrogen-Doped Graphene Grown Using Direct Microwave Plasma-Enhanced Chemical Vapor Deposition

Chemical vapor deposition (CVD) is an attractive technique which allows graphene with simultaneous heteroatom doping to be synthesized. In most cases, graphene is grown on a catalyst, followed by the subsequent transfer process. The latter is responsible for the degradation of the carrier mobility and conductivity of graphene due to the presence of the absorbants and transfer-related defects. Here, we report the catalyst-less and transfer-less synthesis of graphene with simultaneous nitrogen doping in a single step at a reduced temperature (700 °C) via the use of direct microwave plasma-enhanced CVD. By varying nitrogen flow rate, we explored the resultant structural and chemical properties of nitrogen-doped graphene. Atomic force microscopy revealed a more distorted growth process of graphene structure with the introduction of nitrogen gas—the root mean square roughness increased from 0.49 ± 0.2 nm to 2.32 ± 0.2 nm. Raman spectroscopy indicated that nitrogen-doped, multilayer graphene structures were produced using this method. X-ray photoelectron spectroscopy showed the incorporation of pure pyridinic N dopants into the graphene structure with a nitrogen concentration up to 2.08 at.%.

Performance Improvement of Residue-Free Graphene Field-Effect Transistor Using Au-Assisted Transfer Method

We report a novel graphene transfer technique for fabricating graphene field-effect transistors (FETs) that avoids detrimental organic contamination on a graphene surface. Instead of using an organic supporting film like poly(methyl methacrylate) (PMMA) for graphene transfer, Au film is directly deposited on the as-grown graphene substrate. Graphene FETs fabricated using the established organic film transfer method are easily contaminated by organic residues, while Au film protects graphene channels from these contaminants. In addition, this method can also simplify the device fabrication process, as the Au film acts as an electrode. We successfully fabricated graphene FETs with a clean surface and improved electrical properties using this Au-assisted transfer method.

Bifunctional 1-Boc-3-Iodoazetidine Enhancing Lithium Anode Stability and Rechargeability of Lithium-Oxygen Batteries

Lithium anode protection is an effective strategy to prohibit the continuous loss of redox mediators (RMs) resulting from the unfavorable "shuttle effect" in lithium-oxygen batteries. In this work, an in situ Li anode protection method is designed by utilizing an organic compound, 1-Boc-3-iodoazetidine (BIA), as both a RM and an additive, to form a lithium anode protective layer. The reaction between Li metal and BIA can form lithium iodide (LiI) and lithium-based organometallic. LiI can effectively reduce the charging overpotential. Meanwhile, the in situ-formed anode protection layer (lithium-based organometallic) can not only effectively prevent RMs from being reduced by the lithium metal, but also inhibit the growth of lithium dendrites. As a result, the lithium-oxygen battery with BIA shows a long cycle life of 260 cycles with a notably reduced charging potential. In particular, the battery with BIA achieves an excellent lifespan of 160 cycles at a large current density of 2000 mA g^-1.

Significant role of thorny surface morphology of polyaniline on adsorption of triiodide ions towards counter electrode in dye-sensitized solar cells

Revealing the adsorption behavior of polyaniline with thorny surface morphology towards triiodide ions and its impact on the dye-sensitized solar cell performance.

Layer-engineered large-area exfoliation of graphene

The competition between quality and productivity has been a major issue for large-scale applications of two-dimensional materials (2DMs). Until now, the top-down mechanical cleavage method has guaranteed pure perfect 2DMs, but it has been considered a poor option in terms of manufacturing. Here, we present a layer-engineered exfoliation technique for graphene that not only allows us to obtain large-size graphene, up to a millimeter size, but also allows selective thickness control. A thin metal film evaporated on graphite induces tensile stress such that spalling occurs, resulting in exfoliation of graphene, where the number of exfoliated layers is adjusted by using different metal films. Detailed spectroscopy and electron transport measurement analysis greatly support our proposed spalling mechanism and fine quality of exfoliated graphene. Our layer-engineered exfoliation technique can pave the way for the development of a manufacturing-scale process for graphene and other 2DMs in electronics and optoelectronics.

Role of nanowire length on the performance of a self-driven NIR photodetector based on mono/bi-layer graphene (camphor)/Si-nanowire Schottky junction

In this article, we have demonstrated a solid carbon source such as camphor as a natural precursor to synthesize a large area mono/bi-layer graphene (MLG) sheet to fabricate a nanowire junction-based near infrared photodetectors (NIRPDs). In order to increase the surface-to-volume ratio, we have developed Si-nanowire arrays (SiNWAs) of varying lengths by etching planar Si. Then, the camphor-based MLG/Si and MLG/SiNWAs Schottky junction photodetectors have been fabricated to achieve an efficient response with self-driven properties in the near infrared (NIR) regime. Due to a balance between light absorption capability and surface recombination centers, devices having SiNWAs obtained by etching for 30 min shows a better photoresponse, sensitivity and detectivity. Fabricated NIRPDs can also be functioned as self-driven devices which are highly responsive and very stable at low optical power signals up to 2 V with a fast rise and decay time of 34/13 ms. A tremendous enhancement has been witnessed from 36 μA W^-1 to 22 mA W^-1 in the responsivity at 0 V for MLG/30 min SiNWAs than planar MLG/Si PDs indicating an important development of self-driven NIRPDs based on camphor-based MLG for future optoelectronic devices.

A uniform stable P-type graphene doping method with a gold etching process

Graphene is one of the materials with the most potential for post-silicon electronics because of its outstanding electrical, optical, and mechanical properties. However, the lack of a uniform stable doping method extremely limits the various possible applications of graphene. Here, we developed a uniform and stable graphene efficient p-doping method. Through etching a thin gold film on graphene with a KI/I₂ solution, iodine complexes are produced as the dopant absorbing on the graphene surface, and induce extra holes in graphene. Utilizing this method, the graphene film can be effectively doped to p-type without producing undesirable defects, and the roughness of the graphene surface can still be maintained at an ultra-low nanoscale (RMS roughness ∼0.739 nm). The doping effectiveness can be clearly verified by the changes in the Raman spectrum, and the Dirac point shift of the graphene-based transistor, and the reduction of sheet resistance (∼27.2%). Furthermore, the substantially coincident transfer curves after 45 days reveal the long-term stable doping effects. Therefore, this doping method can exploit a way for various graphene-based applications, such as phototransistors, sensors, and organic thin-film transistors.

Immobilization of Polyiodide Redox Species in Porous Carbon for Battery-Like Electrodes in Eco-Friendly Hybrid Electrochemical Capacitors

Hybrid electrochemical capacitors have emerged as attractive energy storage option, which perfectly fill the gap between electric double-layer capacitors (EDLCs) and batteries, combining in one device the high power of the former and the high energy of the latter. We show that the charging characteristics of the positive carbon electrode are transformed to behave like a battery operating at nearly constant potential after it is polarized in aqueous iodide electrolyte (1 mol L⁻¹ NaI). Thermogravimetric analysis of the positive carbon electrode confirms the decomposition of iodides trapped inside the carbon pores in a wide temperature range from 190 °C to 425 °C, while Raman spectra of the positive electrode show characteristic peaks of I₃⁻ and I₅⁻ at 110 and 160 cm⁻¹, respectively. After entrapment of polyiodides in the carbon pores by polarization in 1 mol L⁻¹ NaI, the positive electrode retains the battery-like behavior in another cell, where it is coupled with a carbon-based negative electrode in aqueous NaNO₃ electrolyte without any redox species. This new cell (theiodide-ion capacitor) demonstrates the charging characteristics of a hybrid capacitor with capacitance values comparable to the one using 1 mol L⁻¹ NaI. The constant capacitance profile of the new hybrid cell in aqueous NaNO₃ for 5000 galvanostatic charge/discharge cycles at 0.5 A g⁻¹ shows that iodide species are confined to the positive battery-like electrode exhibiting negligible potential decay during self-discharge tests, and their shuttling to the negative electrode is prevented in this system.

Controlled Island Formation of Large-Area Graphene Sheets by Atmospheric Chemical Vapor Deposition: Role of Natural Camphor

Camphor-based mono-/bilayer graphene (MLG) sheets have been synthesized by very facile atmospheric chemical vapor deposition processes on Si/SiO2, soda lime glass, and flexible polyethylene terephthalate films. The effect of camphor concentration with respect to distance between camphor and the Cu foil (D) has been varied to investigate the controlled formation of a homogeneous graphene sheet over a large area on Cu foil. Raman studies show a remarkable effect of camphor at a typical distance (D) to form a monolayer to multilayer graphene (MULG) sheet. The signature of MLG to MULG sheets appears due to increase in the number of nucleation sites, even over the subsequent domains that contribute stacks of graphene over each other as observed by high-resolution transmission electron microscopy images. Moreover, the increase in camphor concentration at a particular distance generates more defect states in graphene as denoted by D band at 1360 cm-1. Uniform distribution of large-area MLG demonstrates an intense 2D/G ratio of ∼2.3. Electrical and optical measurements show a sheet resistance of ∼1 kΩ/sq with a maximum transmittance of ∼88% at 550 nm for low camphor concentration. An improvement in the rectification and photodiode behavior is observed from the diodes fabricated on n-Si/MULG as compared to n-Si/MLG in dark and light conditions.

Iodine-doped sulfurized polyacrylonitrile with enhanced electrochemical performance for room-temperature sodium/potassium sulfur batteries

Iodine-doped sulfurized polyacrylonitrile with high conductivity displays an unprecedented capacity for RT-Na/S and RT-K/S batteries operated in ester-based electrolytes.

Exploration of Dextran for Application as Corrosion Inhibitor for Steel in Strong Acid Environment: Effect of Molecular Weight, Modification, and Temperature on Efficiency

The possibility of utilizing dextran as a green corrosion inhibitor for steel in strong acid environment was explore using weight loss, electrochemical (electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM), potentiodynamic polarization (PDP), and linear polarization (LPR)) supported with surface analysis via scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) techniques. The effect of molecular weight, temperature, and modification on the inhibition efficiency of dextran was also studied. Results from all the applied techniques reveal that dextran exhibit moderate anticorrosion property toward St37-2 steel dissolution in 15% H₂SO₄ solution. Dextran with molecular weight of 100 000-200 000 g/mol (Dex 1) exhibited the highest inhibition efficiency of 51.38% at 25 °C. Based on PDP results, dextran behaved as a mixed type corrosion inhibitor. Inhibition efficiency of dextran varies inversely with molecular weight but directly with temperature. Two modification approaches, namely incorporation of silver nanoparticles (AgNPs) into dextran matrices and combination with 1 mM KI were adopted to enhance the inhibition efficiency of dextran and the approaches proved effective. The protective capability of Dex 1 has been upgraded from 51.38% to 86.82% by infusion of AgNPs and to 94.21% by combination with KI at 25 °C. Results from the study on the effect of temperature reveals that Dex 1 + KI mixture could synergistically offer 99.4% protection to St37-2 steel in 15% H₂SO₄ environment at 60 °C. Surface analysis results confirm the presence of additives molecules on the studied metal surface. XPS results disclose that AgNPs are in oxide form while iodide ions are in the form of triiodide and pentaiodide ions on the metal surface. Modified dextran is a promising candidate for application as corrosion inhibitor in acid induced corrosive environment.

Center-iodized graphene as an advanced anode material to significantly boost the performance of lithium-ion batteries

Iodine edge-doped graphene can improve the capacity and stability of lithium-ion batteries (LIBs). Our theoretical calculations indicate that center-iodization can further significantly enhance the anode catalytic process. To experimentally prove the theoretical prediction, iodine-doped graphene materials were prepared by one-pot hydrothermal and ball-milling approaches to realize different doping-sites. Results show that the center-iodinated graphene (CIG) anode exhibits a remarkably high reversible capacity (1121 mA h g-1 after 180 cycles at 0.5 A g-1), long-cycle life (0.01% decay per cycle over 300 cycles at 1 A g-1) and high-rate capacity (374 mA h g-1 after 800 cycles at 8 A g-1), which greatly improves the performance of the edge-iodinated graphene anode and these results are in good agreement with the theoretical analysis. More importantly, the CIG anode also delivers a high-rate capacity and excellent cycling stability (279 mA h g-1 after 500 cycles at 10 A g-1) in full-cells. Both the theoretical analysis and experimental investigation reveal the enhancement mechanism, in which the center-iodization increases the surface charge for fast electron transfer rate, improves the conductivity for charge transport and rationalizes the pore structure for enhanced mass transport and ion insertion/desertion, thus resulting in a high rate capacity and long cycle life. This work not only discloses the critical role of catalytic sites including both amounts and site positions but also offers great potential for high-power rechargeable LIB applications.

An in situ iodine-doped graphene/silicon composite paper as a highly conductive and self-supporting electrode for lithium-ion batteries

A highly conductive, highly flexible, self-supporting, and binder-free rGO/Si composite paper with superior electrochemical performance was obtainedvia in situiodine doping and used as electrodes for flexible LIBs.

Novel iodine-doped reduced graphene oxide anode for sodium ion batteries

It is reported for the first time that iodine-doped reduced graphene oxide (I-rGO) has been designed as an anode material for sodium ion batteries (SIBs).

Modulating the electronic and magnetic properties of graphene

Graphene, an sp²hybridized single sheet of carbon atoms organized in a honeycomb lattice, is a zero band gap semiconductor or semimetal.

Graphene-Iodine Nanocomposites: Highly Potent Bacterial Inhibitors that are Bio-compatible with Human Cells

Graphene-composites, capable of inhibiting bacterial growth which is also bio-compatible with human cells have been highly sought after. Here we report for the first time the preparation of new graphene-iodine nano-composites via electrostatic interactions between positively charged graphene derivatives and triiodide anions. The resulting composites were characterized by X-ray photoemission spectroscopy, UV-spectroscopy, Raman spectroscopy and Scanning electron microscopy. The antibacterial potential of these graphene-iodine composites against Klebsiella pneumonia, Pseudomonas aeruginosa, Proteus mirobilis, Staphylococcus aureus, and E. coli was investigated. In addition, the cytotoxicity of the nanocomposite with human cells [human white blood cells (WBC), HeLa, MDA-MB-231, Fibroblast (primary human keratinocyte) and Keratinocyte (immortalized fibroblast)], was assessed. DGO (Double-oxidizes graphene oxide) was prepared by the additional oxidation of GO (graphene oxide). This generates more oxygen containing functional groups that can readily trap more H⁺, thus generating a positively charged surface area under highly acidic conditions. This step allowed bonding with a greater number of anionic triiodides and generated the most potent antibacterial agent among graphene-iodine and as-made povidone-iodine (PVP-I) composites also exhibited nontoxic to human cells culture. Thus, these nano-composites can be used to inhibit the growth of various bacterial species. Importantly, they are also very low-cytotoxic to human cells culture.

Doping-Induced Carrier Density Modulation in Polymer Field-Effect Transistors

Controlled device parameters of high-mobility polymer field-effect transistors (FETs) are demonstrated by modest doping and charge compensation. Through fleeting chemical vapor treatments of aligned poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)-alt-[1,2,5]thiadiazolo-[3,4-c]pyridine] (PCDTPT) thin films as the charge transport layer in the FET channel, the FET properties are tailored by controlling doping concentration of the PCDTPT adjacent to metal electrodes.

Effects of halogen doping on nanocarbon catalysts synthesized by a solution plasma process for the oxygen reduction reaction

Halogen (F, CI, and Br)-containing carbon materials were successfully synthesized by solution plasma process. The effects of halogen doping on chemical structure and electrocatalytic activity were investigated.

Toward graphene chloride: chlorination of graphene and graphene oxide

Chlorinated graphene derivates with chlorine concentration exceeding 11 at% were synthesized by high temperature exfoliation in chlorine atmosphere. Halogen graphenes have a great potential for electronic and electrochemical devices.

Co-Doping of Activated Graphene for Synergistically Enhanced Electrocatalytic Oxygen Reduction Reaction

Doping of graphene has emerged as a key strategy to improve the electrocatalytic performance of the oxygen reduction reaction (ORR). Activated graphene co-doped with iodine and nitrogen atoms (NIG) was developed in this work using a facile scalable approach. The onset potential, current density, and four-electron reduction pathway of the newly developed catalyst were significantly improved. The charge-transfer resistance of co-doped NIG was found to be much lower than nitrogen-doped graphene (NG); furthermore, the stability of NIG and its resistance to methanol crossover were also improved. The synergistically enhanced ORR performance of NIG was found to be a result of a high strain and size advantage of the larger iodine atom clusters (compared to nitrogen), which facilitate the simultaneous enrichment of anode electrons and O2 and H2 O molecule transport at catalytic sites, inducing four-electron transfer in a single step. These results are promising for application in alkaline fuel cells.

Towards graphene iodide: iodination of graphite oxide

Halogenated graphene derivatives are interesting owing to their outstanding physical and chemical properties. In this paper, we present various methods for the synthesis of iodinated graphene derivatives by the iodination of graphite oxides prepared according to either the Hummers or Hofmann method. Both graphite oxides were iodinated by iodine or hydroiodic acid under reflux or in an autoclave at elevated temperatures (240 °C) and pressures (over 100 bar). The influence of both graphite oxide precursors on the properties of resulting iodinated graphenes was investigated by various techniques, including SEM, SEM-EDS, high-resolution XPS, FTIR, STA, and Raman spectroscopy. Electrical resistivity was measured by a standard four point technique. In addition, the electrochemical properties were investigated by cyclic voltammetry. Although the iodinated graphenes were structurally similar, they had remarkably different concentrations of iodine. The most highly iodinated graphenes (iodine concentration above 30 wt%) exhibited relatively high C/O ratios, confirming high degrees of reduction. Iodine is incorporated in the form of covalent bonds to carbon atoms or as polyiodide anions non-covalently bonded through the charge transfer reaction with the graphene framework. Iodinated graphenes with such properties could be used as the starting material for further chemical modifications or as flame-retardant additives.

Theoretical study of polyiodide formation and stability on monolayer and bilayer graphene

Insights of DFT calculations on the formation of polyiodide complexes and their thermal stability on graphene based nanostructures.

Enhanced photoelectrochemical and photocatalytic performance of iodine-doped titania nanotube arrays

The paper discusses the synthesis and performance of iodine doped titania nanotube arrays exhibited under irradiation.

Heteroatom substituted and decorated graphene: preparation and applications

The electronic structure and surface chemistry of graphene can be tuned subtly by doping with heteroatoms, which induces unique applications.

Semimetallic-to-metallic transition and mobility enhancement enabled by reversible iodine doping of graphene

We demonstrate that a reversible semimetallic-to-metallic transition can be realized in monolayer graphene by iodine doping and dedoping processes. Upon iodine doping, the charge transfer from graphene to iodine creates a high hole density up to 4.75 × 10(13)cm(-2), well beyond that realized by applying gate voltages. Iodine-doped graphene shows metallic behaviour, as evidenced by the resistance variation with temperature and magnetic field. We further introduce an iodine dedoping method to completely remove the iodine anions from graphene surfaces. Transport measurements show that after dedoping treatments, the mobility of graphene is significantly enhanced, much higher than that of pristine graphene. The improvement in graphene electronic properties is attributed to the corrosive characteristic of iodine that it can react with and remove absorbed atoms on graphene surfaces. Our work not only opens a facile and effective way to tune the properties of monolayer graphene reversibly, but also demonstrates a new method to increase the quality of graphene.

Heteroatom-doped graphene materials: syntheses, properties and applications

Heteroatom doping endows graphene with new or improved properties and greatly enhances its potential for various applications.

Synthesis, Characterization, In Vitro Phantom Imaging, and Cytotoxicity of A Novel Graphene-Based Multimodal Magnetic Resonance Imaging - X-Ray Computed Tomography Contrast Agent

Graphene nanoplatelets (GNPs), synthesized using potassium permanganate-based oxidation and exfoliation followed by reduction with hydroiodic acid (rGNP-HI), have intercalated manganese ions within the graphene sheets, and upon functionalization with iodine, show excellent potential as biomodal contrast agents for magnetic resonance imaging (MRI) and computed tomography (CT). Structural characterization of rGNP-HI nanoparticles with low- and high-resolution transmission electron microscope (TEM) showed disc-shaped nanoparticles (average diameter, 200 nm, average thickness, 3 nm). Energy dispersive X-ray spectroscopy (EDX) analysis confirmed the presence of intercalated manganese. Raman spectroscopy and X-ray diffraction (XRD) analysis of rGNP-HI confirmed the reduction of oxidized GNPs (O-GNPs), absence of molecular and physically adsorbed iodine, and the functionalization of graphene with iodine as polyiodide complexes (I₃^- and I₅^-). Manganese and iodine content were quantified as 5.1 ± 0.5 and 10.54 ± 0.87 wt% by inductively-coupled plasma optical emission spectroscopy and ion-selective electrode measurements, respectively. In vitro cytotoxicity analysis, using absorbance (LDH assay) and fluorescence (calcein AM) based assays, performed on NIH3T3 mouse fibroblasts and A498 human kidney epithelial cells, showed CD₅₀ values of rGNP-HI between 179-301 µg/ml, depending on the cell line and the cytotoxicity assay. CT and MRI phantom imaging of rGNP-HI showed high CT (approximately 3200% greater than HI at equimolar iodine concentration) and MRI (approximately 59% greater than equimolar Mn²⁺ solution) contrast. These results open avenues for further in vivo safety and efficacy studies towards the development of carbon nanostructure-based multimodal MRI-CT contrast agents.

Halogenated graphenes: rapidly growing family of graphene derivatives

Graphene derivatives containing covalently bound halogens (graphene halides) represent promising two-dimensional systems having interesting physical and chemical properties. The attachment of halogen atoms to sp(2) carbons changes the hybridization state to sp(3), which has a principal impact on electronic properties and local structure of the material. The fully fluorinated graphene derivative, fluorographene (graphene fluoride, C1F1), is the thinnest insulator and the only stable stoichiometric graphene halide (C1X1). In this review, we discuss structural properties, syntheses, chemistry, stabilities, and electronic properties of fluorographene and other partially fluorinated, chlorinated, and brominated graphenes. Remarkable optical, mechanical, vibrational, thermodynamic, and conductivity properties of graphene halides are also explored as well as the properties of rare structures including multilayered fluorinated graphenes, iodine-doped graphene, and mixed graphene halides. Finally, patterned halogenation is presented as an interesting approach for generating materials with applications in the field of graphene-based electronic devices.

Molecular iodine/polymer complexes

A unique feature of molecular iodine by far, is its ability to bind to polymeric materials. A plethora of natural and synthetic polymers develop complexes when treated with molecular iodine, or with a mixture of molecular iodine and potassium iodide. Many unexpected findings have been encountered upon complexation of iodine and the polymer skeleton, including the color formation, the polymer morphology changes, the complexation sites or regions, the biological activity, and the electrical conductivity enhancement of the complexes, with polyiodides (In¯), mainly I3¯ and I5¯, as the actual binding species. Natural polymers that afford such complexes with iodine species are starch (amylose and amylopectin), chitosan, glycogen, silk, wool, albumin, cellulose, xylan, and natural rubber; iodine-starch being the oldest iodine-natural polymer complex. By contrast, numerous synthetic polymers are prone to make complexes, including poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP), nylons, poly(Schiff base)s, polyaniline, unsaturated polyhydrocarbons (carbon nanotubes, fullerenes C60/C70, polyacetylene; iodine-PVA being the oldest iodine-synthetic polymer complex.